The subject invention relates to magnetic recording systems and particularly to improved techniques and arrangements for interrelating transducer-actuators with disk stacks.
Workers in arts involving the design, manufacture and/or use of magnetic recording systems will recognize the need for improved techniques and associated apparatus for more efficient, more accurate data storage/read-out functions. One particular need-- evermore demanding-- is for a "mass store" system adapted for automatic data processing. This invention is intended to provide an improved mass store system of this type; one making better, more efficient use of recording surfaces and of associated transducer access means.
Prior art approaches:
Workers will recognize that various types of storage media have long been considered for "mass store"; such as "surface deformation" media; "photo-recording" media and magnetic recording media. One form of photo-recording mass store system involved a so-called "trillion bit photo digital" system. Here, recording was photographic, on a silver halide film dispersed upon a rigid glass carrier. After exposing and processing, these film-carriers were stored near a Read-station and pneumatically transported to the station when called-up.
However, magnetic recording media are now preferred for various reasons; for instance, they are updated very easily and conveniently. Magnetic recording media is either "rigid" (disks or drums) or flexible-- the latter, including "floppy disks" and magnetic tape (strip, reel, loop, etc.), are usually preferred because of their aptness for efficient, low-cost, high-capacity storage.
Now, as workers well know, adapting flexible magnetic recording media for mass storage can conceiveably involve either a large pack of flexible disks (e.g., advantageous for random access manipulation) or tape-- either in reel, cartridge or strip form, or as a continuous loop. Workers also recognize that transducing may be performed along such media in either a longitudinal or a "rotary" transducing mode. Disks are typically accessed by a moving-arm transducer mechanism; whereas tape is accessed by (one or several), transport mechanisms. The present invention is intended to implement mass store systems with flexible magnetic recording media.
Other flexible magnetic media:
Workers will recall various other flexible-media approaches suggested for data storage. For instance, one concept involved "Data Cells" comprising longitudinal magnetic recording strips having data capacities on the order of several billion bytes, or more and using thick magnetic strips, (e.g., a few inches by about a foot by a foot by a few mils) on which data was to be longitudinally recorded. The Data Cells were modular; with several cell drives being under the aegis of a common control unit. Access times as short as several hundred milliseconds were projected.
Another concept involved flexible spooled-cartridges (see "Magnetic Recording Storage" by Hoagland in IEEE Computer Transactions of December 1976). These cartridges were to be transported from a "storage-honeycomb" to Read/Write stations where "rotary-head" transducing was postulated. This flexible medium was chosen to maximize "volumetric-density" (information stored per unit volume of the apparatus)-- the cost alone of rigid media being prohibitive by comparison.
Another flexible media approach involved the use of flexible magnetic recording disks, arranged as a "cluster" of disks packs adapted to be accessed by a single common transducer mechanism. (See U.S. Pat. No. 3,703,713 to Pohm and Zingg issued Nov. 21, 1972). A very large rather slow and ponderous "archival" type storage memory was contemplated here (capacity of 10.sup.12 bits). In each pack the disks were subdivided into groups; the disks in each group all had different, increasing diameters. These disks were to be mechanically partitioned, from without, by a knife-like transducer arm which mechanically diverted adjacent disks from the "target disk" (surface)-- though such physical contact is well recognized as highly undesireable. In a specific embodiment contemplated, eight cylindrical packs each four feet long were proposed for access by a single, centrally-located mechanism. This invention contemplates an improved mass storage system comprised of flexible disk packs which are arranged in short paired stacks arranged to share an associated pair of transducer actuator devices.
Conventional "mass-store" architecture:
Workers will recognize that an optimal "mass store" system (MSS) will provide memory capability for handling all data at a given user-establishment in a fully automated manner. The key to cost-effective implementation is to provide a low-cost, high-capacity mass storage memory (MSM) which is CPU accessed very quickly. Also, it should be effectively integrated with any other related memory stages, such as archival memory, direct-access memory and "working" memory-- in effect vastly expanding D-A memory. The present invention is intended to provide this in a novel mass store system and related subsystems.
A typical present-day mass storage system (e.g., massive tape file) operates too slowly and inefficiently; being characterized by manual intervention and/or staging-destaging indirect (buffered) CP access and associated high storage/access costs and slow access. For instance, when the processor of a typical system requests a "data set" which is not stored in the system's D-A memory, (typically a disk file), an operator must be instructed, via a SPO (i.e., a "Simultaneous Peripheral Operation"; e.g., on a high-priority operator terminal), to fetch the tape reel containing this data-set from his tape library; then the operator must mount this reel on a tape transport and "stage" it into the direct-access memory (e.g., rigid-disk file) of the MSS. Further, if the data-set is to be modified, it must be "de-staged" to tape for library-return. Such systems are, of course, rife with manual intervention and much too slow-- averaging only about 10 reel-mountings per hour per tape transport-- a rate which is intolerably slow and unrealistically crude compared with what can be achieved by automation, as workers know. Such automation has been proposed (e.g., see Hoagland art above and; Harris "Mass Store System" IEEE Proc. 8/75). One proposed tape system is characterized by the equivalent of about 146 reel-mountings per hour for staging average-sized data sets. There is no way that such a plethora of tape cartridges can be efficiently handled manually.
According to this invention this problem is attacked with flexible disk packs, rather than tape. For instance, in a system of the type described in the preferred embodiment below, access to an average data-set is feasible at the rate of about 600 to 700 mountings per hour-- being characterized by faster disk-accessing as well as cost advantages, with a speed/cost ratio which is very, very significant. [E.g., assume that it costs about $3.00 to store one reel for one year and about $2.50, and several minutes for each mounting or de-mounting vs. a fraction of a second for comparable disk-access. Here, direct access alone by eliminating staging/destaging can save close to one second].
It will be understood that the architectural scheme 1. indicated in FIG. 3 is intended to present a data record from MSM to a readily useable "data block path" R, adjacent a "working memory unit". Such a call-up (path) is completely impractical in tape systems of the type described, whereas in disk systems like those proposed, it is quite feasible because of the associated shorter data access time.
This invention addresses the foregoing problems in a new way, teaching the provision of a MS system with pairs of relatively short compact stacks of "floppy disks", each pair of stacks preferably having its own shared pair of actuator assemblies-- this in a fast-access, direct-access MS Memory directly and automatically linked to an automatic data processing system, including other memory, without "staging" or like intervention. The low cost, compactness, and fast-access of such floppy disk modules will be seen as providing improved MS Memory with capacities of several dozen BB (billion bytes) and more.